Teenage Mutant Ninja Frogs! The Long-term Effect of Radiation on Chernobyl Tree Frogs

By: Stephen Cobbs, John de Abreu, Clare Feeman, and Molly Turner (Stonehill College, BIO323: Evolution, Spring 2022)

On April 26, 1986, the world effectively changed in the blink of an eye. An accident during a technical test at the Chernobyl Nuclear Power Plant near the city of Slavutych, Ukraine, produced what would eventually be referred to as “the worst nuclear disaster in history”. The consensus on the immediate, short-term effect of the accident was undeniably poor, as all wildlife within the area suffered mass casualties. 36 years later however, and the consensus is rather murky. Scientists have recently visited the Chernobyl Exclusion Zone (CEZ) and were shocked to find that area today presents great biodiversity, playing host to a multitude of different species from a multitude of different clades. Why is that you may ask? Well, some scientists believe that the radioactive pollution from the nuclear fallout led to an increase in mutation rates within genes of the animals in Chernobyl, which partially offset the diversity which was initially lost. This raises the question if there is such a thing as too many mutations and is there a line at which mutation rates cross from beneficial to deleterious? The paper Unusual evolution of tree frog populations in the Chernobyl exclusion zone, by Clément Car and 11 others, works to classify those questions, specifically looking at populations of Eastern Tree Frogs (Hyla orientalis) both in and around the CEZ and using simulations for populations throughout Europe as a whole.

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How does Radiation Accelerate Evolution?

By: Kristina McEvoy, Eli Penza-Clyve, Amaya Toribio, and Lindsey Walsh (Stonehill College, BIO323: Evolution, Spring 2022)

Have you ever wondered how wildlife has been affected by the 1986 Chernobyl nuclear power plant explosion? The disaster has been a subject of fascination to many, inspiring media such as the 2012 horror film Chernobyl Diaries and HBO’s 2019 television miniseries, Chernobyl. Although the incident occurred a little over 35 years ago, the accident has left lasting effects on the creatures that inhabit the Chernobyl area, particularly in the realm of genetic mutations.

Researchers at the University of Stirling, in collaboration with the Ukrainian Hydrometeorological Institute in Kyiv, sought to determine how radiation affected genetic diversity in a freshwater crustacean living in lakes at varying distances to the disaster. Daphnia pulex, also known as water fleas, live in the seven lakes examined in this study; five lakes were within the Chernobyl Exclusion Zone, or the radioactive area surrounding the explosion site, and two were located outside this boundary. Water fleas are known to accumulate mutations and suffer from a reduced ability to survive and reproduce when exposed to radiation. Scientists investigated the variation between the water fleas at each location by extracting DNA and sequencing ten microsatellite gene locations on chromosomes. Essentially, microsatellites are short segments of repeated DNA motifs in many places within one’s genome. The variation in the length of these microsatellites can serve as a measure of genetic diversity. The radiation from Chernobyl can lead to the development of genetic mutations, which can, in turn, increase genetic diversity. However, this relationship can change drastically when taking other evolutionary factors into account. Considering the radioactive conditions, there are two possible outcomes: either mutations cause genetic diversity to increase, or natural selection eliminates individuals that cannot survive the cellular damage associated with radiation, thus decreasing genetic diversity.

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